1. Field of the Invention
This invention relates to a system for transmitting signals between a plural number of input/output devices, or more particularly, to a signal transmission system which is improved to reduce drastically the number of signal lines connecting input/output devices.
2. Description of the Prior Art
Generally, known signal transmission systems transmit signals between a plural number of input/output devices by connecting each input/output device to every other input/output device with a separate signal line. Additionally, signal transmission systems are known in which identifying signals which direct the destination of input/output signals are transmitted simultaneously with the input/output signals. That is, the destination of each input/output signal is decided by distributing both the input/output signal and identifying signal to other input/output devices.
However since both these conventional signal transmission systems have required for example, two times as many signal lines as the number of the input/output devices, they have the disadvantage, that the wiring between input/output devices is complex. The configuration of the signal lines as well as the entire signal transmission system becomes cumbersome and the the reliability of signal transmission is reduced.
FIG. 1 shows an example of a signal transmission system of conventional type. The exemplary configuration illustrated shows the case in which signal transmission is made between the devices I, II, and III. In FIG. 1, 11, 12, and 13 show respectively the devices I, II, and III, 111, 121, and 131 are arithmetic units forming a part respectively of the devices I, II, and III, and 112, 113; 122, 123;, 132, 133; 114, 115; 124, 125; and 134, 135 are driving sections and receiving sections for input/output signals respectively going from the arithmetic units of each device to other devices or coming from other devices to the arithmetic units of each device. 14 is a plural number of pairs of signal lines which individually connect each of these driving sections with each of these receiving sections, in which a, b, c, d, e, and f show respectively a pair of signal lines. For example, the signal line a is a pair of signal lines used for signal starting from the arithmetic unit 111 of the device I, passing through the driving section 112 and receiving section 124 sequentially, and arriving at the arithmetic unit 121 of the device II. Accordingly the signal lines used in the illustrated configuration comprise 6 pairs a through f two times as many in number as the number of devices namely 3. As has been described so far in the conventional signal transmission system, the configuration of signal lines connecting the devices to one another is very complicated.